The negative dynamic icon is represented by three rectangular bars going from taller to very short. The bars are next to each other, with some space in between, with the tallest bar on the left. Above the three bars is an arrow point down, running along the same downward angle as the 3 bars. The arrow is a single line drawing.

This page shows the different variations of the Decline from an Icons8 icon pack. Feel free to resize and recolor the icon, and then download the icon in PNG format for free.